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    let arr = [1, 2, 3, 4, 5]
    function sum(a, b = true) {
      let add = 0
      for (let i = 0; i < a.length; i++) {
          add += a[i]
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        return add
      }else {
        return ( add / a.length )
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    console.log(sum(arr , false));
  
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